This invention addresses the fact that in power generation (power plants, combustion engines, combustion devices, refineries, industry) significant amounts of valuable energy are lost through hot exhaust gases.
A system using a steam turbine to convert the heat in said exhaust gases into useful energy, for example electrical energy, is established and proven technology. A steam turbine could extract thermal energy from exhaust gases independently of any ORC. However, this would require cooling of the steam exiting the steam turbine, and typically requires large and expensive condensation vessels operating under vacuum.
It is also technically feasible to extract more heat from exhaust gases, and to use such heat e.g. at 90° C. in Rankine cycles. However, at low temperatures corrosive substances will condense during heat extraction, possibly leading to severe corrosion problems. Ideally, usage of low temperatures for energy recovery is combined with proper methods for removal of sulfur, nitrogen oxides and other corrosives.
The disclosures and references presented below give a general picture of power plant technology and waste heat recovery systems.
US2013 0341 929A1 by Ralph Greif (University of California) et al describes a variation of the ORC cycle, referred to as Organic Flash Cycle. The authors describe general problems associated with power generation from saturated vapours, see section [0045].
U.S. Pat. No. 8,889,747 by Kevin DiGenova et al (BP, 2011) describes the use of ORC systems in combination with Fischer-Tropsch reactors. U.S. Pat. No. 4,589,258 (Brown Boveri, 1986) discloses general wet steam turbine technology.
U.S. Pat. No. 7,900,431 by George Atkinson et al (Parsons Brinckerhoff, 2006) and U.S. Pat. No. 4,831,817 by Hans Linhardt, 1987, also give interesting general background to wet steam turbine applications.
U.S. Pat. No. 4,455,614 (Westinghouse, 1973) discloses a power plant scheme including a combination of steam turbines and waste heat recovery by employing steam generators.
Various types of steam turbines are available, such as condensing, non-condensing, reheat, extraction and induction types, and the reader is referred to A. Stodola, “Steam and gas turbines”, McGraw Hill, and similar text books.
US20140069098A1 (Mitsubishi, 2012) discloses a power-generating device using an ORC which uses heat recovered from an exhaust gas treated in an exhaust gas treatment device, the power-generating device including a heat exchanger, an evaporator, a steam turbine, a power generator, a condenser, and a medium pump.
US20140352301A1 by Torsten Mueller (GM, 2013) discloses a waste heat recovery system for a motor vehicle.
U.S. Pat. No. 8,850,814 by Uri Kaplan (Ormat, 2009) discloses a waste heat recovery system using jacket cooling heat and exhaust gas heat. Here, jacket cooling heat is used to pre-heat a liquid organic working fluid which later is evaporated using heat from exhaust gases. Said heat is delivered in the form of expanded steam which has passed a steam turbine.